Hey I am in the same boat as you OP. I entered the ARD program and completed it. However, I will say my charges are more serious than yours, and yes I know DUI is a serious charge. I contacted the people who deal with expungement for the State police, and this is what they told me...an ARD is a non conviction and the record has been dismissed under the circumstances that you completed the ARD. However, your arrest and print is still on file.
Now when someone, say a hospital or the BON, runs a background check on an individual, typically if that individual has no record or previous arrest then their record will show up as a "no record" within few minutes of running the background check. In your case you have done ARD and what will show up to the person running the background check will say "under review" under your name. They will get a response ~1 to 2 weeks later clearing you of any record and you will receive a "no record" status.
However, the ~1 to 2 weeks time gap when you are "under review" MIGHT bring up some suspicion on the person running the background check on you, and it's up to them if they want to further dig deeper into your past or not. However, once you get your record expunged then you won't run into this program of being "under review" and instead once you get your record expunged, and if someone did a background check on you then in a matter of minutes it will show up as a "no record".
I am entering nursing school
this fall and was afraid of that same thing. I also live in Pa and have hired an attorney to expunge my record, but it's taking longer than I want. I am just hoping they don't dig deeper and find out I was in the ARD program, but my advisor said ARD isn't as bad as a conviction.